The present invention generally relates to nozzles for forming and directing composite fluid sprays. More specifically, the present invention relates to nozzles for use in solid particle spray systems employing lubricants and dense fluids such as solid carbon dioxide.
Use of composite sprays for lubrication, cooling or both, is widely known in the art. Composite sprays are typically employed during machining processes requiring selective thermal control and/or lubrication during lathe machining, board cutting, wafer singulation or active electronic component thermal cycling. Composite sprays are also employed in high-speed metalworking and machining operations, such as turning, milling, facing, threading, boring and grooving, to extend insert life and provide for more precise machining.
There exist in the art several examples of nozzles which are employed to direct composite sprays onto substrates, work pieces, and the like, in manufacturing or industrial processes. Such examples include U.S. Pat. Nos. 3,985,302, 4,555,059, 4,195,780 and 5,725,154. Each of the aforementioned, however, have shortcomings in the application of composite sprays for lubricating and cooling purposes, more especially the application of cryogenic composite sprays for lubricating and cooling purposes.
Efficient and effective application of cryogenic composite sprays to machined substrates presents several challenges. When sufficiently high spray velocities are employed to provide enough energy to reach cutting zone surfaces, the majority of the spray tends to deflect from or stream around the cutting zone surfaces rather than impinge upon them. When low velocity sprays are employed, critical surfaces with recesses or complex surfaces cannot be penetrated effectively. Also, it is known that oil droplets, evenly finely atomized, tend to agglomerate into larger droplets during transition from spray nozzles to surfaces. This phenomenon interferes with the even distribution of coolants and lubricants on machined surfaces and causes a large portion of the atomized spray to miss the substrate entirely if positioned at a location too far away from the substrate being machined, wasting a portion of the applied spray. More importantly, though, cryogenic composite sprays comprising a lubricating component, such as an oil, and a cooling component, such as liquid/solid carbon dioxide, tend to be the most problematic in applying because the temperatures necessary to employ the coolant cause the lubricant to either solidify, gel or make non-atomizable. This problem is exacerbated when mixing of the cryogenic composite spray occurs within the nozzle, resulting in inconsistent spray patterns and/or the nozzle becoming clogged with agglomerated lubricant or cleaning agent.